This proposal is concerned with the perception and production of temporal regularities. The ability of humans to process information over time can be seen across perceptual and motoric tasks. We are able to perceive rhythmic structure as well as gauge the velocity of moving objects. We can also precisely control the timing of our movements as evidenced by our ability to produce isochronous intervals. Evidence suggests that these timing phenomena involve a common internal clock. Moreover, a common neural mechanism is implicated by the finding that patients with cerebellar lesions are impaired at movement and perceptual tasks which require precise timing. The extended goal of this research program is to provide an account of timing at behavioral, computational, and neural levels of explanation. One set of experiments in this proposal will examine the generality of timing processes involved in perception and movement. The temporal extent of these processes will be explored in three ways. First, psychophysical functions will be determined for temporal acuity with a variety of stimuli. Second, transfer and interference paradigms will determine the interactions and independence of timing mechanisms. Third, patient studies will explore dissociations between lesion foci and deficits on the timing tasks. These experiments are expected to provide converging evidence of a behavioral and neural dissociation between short and long range timing. A second set of experiments will explore constraints on timing functions associated with the cerebellum. One issue is whether there are multiple timing systems associated with this structure or if multiple tasks utilize a single timing system. Healthy subjects will be tested on pairs of tasks which involve temporal processing. Specific patterns of interference between tasks will be indicative of a common processing system. Case studies of selected cerebellar patients will be conducted to identify patterns of associations and dissociations in timing deficits.